This invention relates to multilayer metal foil and metal sheet structures which have utility as heat and acoustic shields and insulating panels.
Multilayer metal foil insulation has been used for many years, as illustrated by U.S. Pat. No. 1,934,174. Such metal foil insulation has typically been used in high temperature applications for reflective heat insulation. In those applications, the layers of metal foils are embossed to provide separation between the layers, and the stack of layers are protected in a container or rigid cover to prevent the stack of metal foils from becoming compressed at any portion, which would decrease the heat insulation value of the stack.
U.S. Pat. No. 5,011,743 discloses that multilayer metal foil insulation can provide enhanced performance as a heat shield when a portion of the multilayer metal foil is compressed to provide a heat sink area through which heat is collected from the insulating portions of the stack and dissipated from the heat shield. Such multilayer metal foil heat shields are formed from a stack of embossed metal foil layers by compressing portions of the stack to create the desired heat sink areas. The layers are attached to each other or stapled together to prevent the layers from separating. The heat shields and acoustic shields formed according to the disclosure of the U.S. Pat. No. 5,011,743 are typically compressed in the heat sink areas and cut to a desired pattern. Such multilayer metal foil heat shields do not normally have sufficient structural strength for stand-alone use in many applications. For many applications, the metal foil heat shields are typically attached to a structural support member or pan to provide a final assembly which is then placed in service as a heat shield or acoustic shield. The support members are typically metal pans, metal stampings or metal castings. Typical applications for such heat shield assemblies include automotive heat shield applications.
U.S. Pat. No. 5,763,857 discloses a heating appliance with a metal foil insulating jacket comprising air tight chambers.
The disclosures of the above patents are incorporated herein by reference.
It is an object of this invention to provide an improved multilayer metal foil insulation structure which is suitable for use in heat shield or heat insulation applications and/or acoustical insulation panel applications.
The corrugated multilayer metal foil structure according to this invention comprises a stack of metal foil layers which is formed from the combination of at least two corrugated layers separated by an intermediate metal foil separation layer, wherein the separation layer is preferably not corrugated, but is relatively flat in nature. Preferably the multilayer metal foil structure comprises at least five layers: three corrugated layers and two separation layers. The multilayer metal foil structure can further comprise an exterior metal foil layer suitable for contact with the body, member or surface on which the insulating structure is applied or suitable for protection of the stack from environmental damage. The channels formed by the corrugations and between a corrugated layer and the adjacent separation layer can be sealed to form elongated isolated air spaces or can be left open at the ends and adapted to act as gas flow conduits through the structure whereby heat can be spread more evenly throughout the structure, or can be directed from a hotter zone to a cooler zone or can be removed from the interior of the structure. The multilayer metal foil structures of this invention provide a wide variety of design options for heat insulation, heat spreading and heat management in any particular application.
In one aspect this invention provides improved insulation and heat management in commercial food preparation ovens, particularly in the gas fired, indirect heated ovens, i.e., wherein the flame and resulting combustion gasses are outside and separate from the food compartment (also known as xe2x80x9cair washxe2x80x9d ovens). Conventional insulation, such as fiber glass, loses its effectiveness over time due to contamination. The multilayer metal foil structure of this invention in combination with food preparation ovens provides ovens of improved performance in terms of uniformity of temperature within the oven and in terms of life cycle of the oven, because the structures of this invention are more durable and need less insulation replacement or repair over time compared to conventional insulation. While the structures of this invention are advantageous in any oven wall insulation, they are particularly preferred for use in air wash ovens to insulate between the exterior wall of the oven cabinet and the heating chamber surrounding the cooking chamber.
This invention further provides methods of making the multilayer metal foil structures by forming the corrugated layers and separation layers in desired configurations and patterns, then assembling the stack of layers with any optional exterior layer desired. In a preferred method of forming the structures of this invention the individual metal layers are continuously supplied from rolls, corrugated, embossed or patterned as desired and assembled continuously into a stack. Then desired parts, pads, panels or other shapes are cut from the stack for final assembly into the end use product, such as ovens, automobiles, and the like, and can be shaped into any desired three dimensional shape before such final assembly.